JP2011189499A - Hard film coated tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the long service life of a hard film coated cutting tool, wherein a first hard film improves abrasion resistance by the realization of high hardness and a second hard film reduces compressive stress and improves adhesion. <P>SOLUTION: In this hard film coated tool, a hard film is covered with the first hard film and the second hard film from a base body surface. The first hard film is indicated by (Al<SB>a</SB>Me<SB>100-a</SB>)<SB>e</SB>N<SB>f</SB>, and here, (a) is atomic%, (e and f) express the atomic ratio, 35≤a≤65 and 0.90≤e/f≤1.15 are realized, Me is one or more of elements selected from 4a, 5a and 6a groups, Si and B, and N is nitrogen. The second hard film is indicated by (Ti<SB>100-h</SB>B<SB>h</SB>)<SB>m</SB>N<SB>p</SB>, and here, (h) is atomic%, (m and p) express the atomic ratio, and 1≤h≤30 and 0.90≤m/p≤1.15 are realized. Assuming respectively spacing (nm) of a (111) surface in X-ray diffraction in the first hard film and the second hard film as d1 and d2, 1.01≤d2/d1≤1.05 is realized. The second hard film has a columnar structure, and a crystal grain of the columnar structure is a composition modulation structure having a composition difference in a B component. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tool used for processing metal parts and the like. In particular, the present invention relates to a hard film-coated tool in which a hard film is coated on a tool surface that requires wear resistance and adhesion using physical vapor deposition (hereinafter referred to as PVD method).

  Patent Document 1 discloses the orientation of the (111) plane and the half-value width of the diffraction peak in X-ray diffraction of a hard film coated by the PVD method. Patent Document 2 discloses a technique for controlling peak intensities on the (220) plane and the (111) plane. Patent Document 3 discloses a technique for adjusting the composition ratio between a metal element and a gas component element constituting a hard coating. Patent Document 4 discloses a technique related to improvement in adhesion at a film interface by epitaxial growth.

JP 2006-281363 A JP 2003-71611 A JP-A-7-188901 JP 2001-181826 A

  The problem to be solved by the present invention is to provide a hard film coated tool excellent in wear resistance by increasing the hardness while ensuring a reduction in compressive stress and adhesion in a hard film having increased thickness.

The present invention relates to a hard film-coated tool in which a hard film having a compressive stress is coated on a substrate with a film thickness of 5 to 30 μm. The hard film is formed from the surface of the substrate by the first hard film and the second hard film. The outermost coating is coated with the second hard coating, and the first hard coating is represented by (Al _a Me _100-a ) _e N _f , where a is atomic%, e and f are Represents an atomic ratio, 35 ≦ a ≦ 65, 0.90 ≦ e / f ≦ 1.15, Me has one or more selected from 4a, 5a, 6a group, Si, B, The second hard coating is represented by (Ti _100-h B _h ) _m N _p , where h is atomic%, m and p are atomic ratios, 1 ≦ h ≦ 30, 0.90 ≦ m / p ≦ 1.15, and the crystal structure of the first hard film and the second hard film is a face-centered cubic structure. When the peak intensity of the (111) plane is Ir, the peak intensity of the (200) plane is Is, and the peak intensity of the (220) plane is It, 0.2 ≦ Is / Ir ≦ 1.4, 0.6 ≦ It / Is ≦ 1.5, and in the X-ray diffraction of the second hard coating, (111) plane peak intensity Iu, (200) plane peak intensity Iv, and (220) plane peak intensity Iw 5 ≦ Iv / Iu ≦ 15 and 2 ≦ Iw / Iv ≦ 4, and the (111) plane spacing (nm) in the X-ray diffraction of the first hard coating and the second hard coating is respectively , D1, and d2, 1.01 ≦ d2 / d1 ≦ 1.05, the second hard film has a columnar structure, and the crystal grains of the columnar structure have a compositional difference in the B component A hard coating tool characterized by a modulation structure. By adopting the above-described configuration, it is possible to provide a hard film-coated tool that is excellent in wear resistance due to high hardness while ensuring a reduction in compressive stress and adhesion in a hard film that has been thickened.

  In the hard film-coated tool of the present invention, a part of the nonmetallic component nitrogen (N) element in the first hard coating is replaced with carbon (C) element and oxygen (O) element, and the entire nonmetallic component is 100, the content of C element in atomic% is x, and the content of O element is y, 0 <x ≦ 10, 0 <y ≦ 10, 0 <x + y ≦ 10, and the content of N element is 100 -Xy is preferable. Further, regarding the Ti element of the metal component in the second hard film, when one part thereof is replaced with silicon (Si) element and the total of the metal component is 100, the content of Si element in atomic% is k, Then, it is preferable that 0 <k ≦ 20 and the content of Ti element is 100-hk. It is more preferable that the hard film having a compressive stress has a thickness of 10 μm to 30 μm.

  According to the present invention, it is possible to provide a hard film coated tool having excellent wear resistance due to high hardness while ensuring a reduction in compression stress and adhesion in a thick hard film.

The first hard film in the hard film-coated tool of the present invention is represented by (Al _a Me _100-a ) _e N _f as a composition, and the a value representing the aluminum (Al) content is in the range of 35 ≦ a ≦ 65. In this case, heat resistance and wear resistance are excellent. If the a value exceeds 65%, the first film cross-sectional structure becomes finer, increasing the compressive stress and deteriorating the adhesion to the substrate. If the a value is less than 35%, there is a disadvantage that the wear resistance is poor. The Me component collectively referred to as the element Me includes elements 4a, 5a, and 6a having an ionic radius of 0.041 to 0.1 nm, silicon (Si) having an ionic radius of 0.002 to 0.04 nm, It is preferable to coat as a nitride containing boron (B) or the like. This is because there is a difference between the ionic radius of the Me component, silicon or boron, and the ionic radius of the aluminum element, and stress acts on the crystal structure, which is convenient for increasing the hardness of the film. By selecting, for example, titanium (Ti) as the Me component, it is effective for increasing the hardness of the first hard coating. For example, when Me is silicon (Si) or boron (B), the content range for maintaining a solid solution is 1% to 20%, and excellent heat resistance and lubrication characteristics can be obtained. Moreover, containing W, Nb, and Cr as Me is effective in improving the heat resistance and hardness of the first hard coating.

  By setting the ratio e / f value between the metal component and the non-metal component of the first hard coating to 0.90 to 1.15, the compressive stress of the hard coating can be set to an optimum range, and high adhesion is achieved. Can be obtained. Further, when the e / f value is 0.90 to 1.15, the structure of the first hard film can be a columnar structure having high toughness, and excellent chipping and wear resistance can be obtained. When the e / f value is 0.85 or more, the crystal lattice strain of the first hard film can be reduced. However, when the e / f value is less than 0.90, the crystal lattice strain increases and the continuity of crystal lattice fringes is lost. The cross-sectional structure of the first hard coating becomes finer and grain boundary defects increase. As a result, the compressive stress is increased and the adhesion is deteriorated. For example, in hard coatings for cutting tools, this grain boundary defect causes a decrease in the density of the hard coating and inward diffusion of the elements constituting the workpiece into the hard coating. Deteriorate. When the e / f value exceeds 1.15, the first hard film has a columnar structure, but it is easy to incorporate impurities into the crystal grain boundary. This impurity is a component remaining inside the apparatus that performs the coating process. As a result, the bonding strength between the crystal grains deteriorates, and the first hard coating is easily broken by an external impact. By setting the first hard coating of the present invention in the range of 0.90 ≦ e / f ≦ 1.15, the compressive stress of the first hard coating is in the range of 1.5 to 5.0 GPa. Industrially, by setting the e / f value within the range of the present invention, it is possible to manage the first hard coating within a range where the compressive stress is not excessive while having the compressive stress.

  When the second hard coating is a nitride having a face-centered cubic structure containing Ti and B, excellent welding resistance can be realized. The h value (atomic%) indicating the B content in the second hard coating is 1 ≦ h ≦ 30. This range of h values is important for making the second hard coating a columnar structure. Moreover, when B element is contained, the wear resistance of the rake face of the tool is improved. In the initial stage of cutting, B is oxidized from the state where the tool edge is still at a low temperature to form a B-containing oxide. This B-containing oxide exhibits the effect of suppressing diffusion of the workpiece component into the second hard coating. However, when the h value exceeds 30%, the structure of the second hard coating becomes finer. In addition, boron nitride (BN) crystals appear and the hardness is lowered, and the compressive stress of the second hard film is increased, resulting in a drawback that adhesion is lowered. An effect appears even if the h value is about 1%.

  Moreover, by setting the ratio m / p value of the metal component and the nitrogen component of the second hard coating to 0.90 to 1.15, the compressive stress of the second hard coating can be set to an optimum range, and high adhesion can be achieved. Sex can be obtained. Further, when the m / p value is 0.90 to 1.15, the second hard film can be made to have a columnar structure having high toughness, and both excellent defectability and wear resistance can be achieved. When the first hard film and the second hard film have a face-centered cubic structure, a hard film having high hardness and excellent wear resistance as a whole can be obtained.

Below, the manufacturing conditions for achieving the composition and structure conditions of the present invention will be described. In the case of (Al _a Me _100-a ) _e N _f which is the first hard film, it is important to control the reaction pressure during film formation in order to make the range 0.90 ≦ e / f ≦ 1.15. It is. In order to obtain a nitride, the reaction pressure of nitrogen is set to 3 Pa to 8 Pa. More preferably, it is good to set it as the range of 3.5 Pa-7Pa. When the reaction pressure is less than 3 Pa, the kinetic energy of ions incident on the substrate becomes high, which appears as crystal lattice strain, and the compressive stress cannot be suppressed. At this time, the e / f value is less than 0.90. When film formation is performed under conditions exceeding 8 Pa, the plasma density decreases and the kinetic energy of incident ions decreases. At this time, the e / f value exceeds 1.15.

  As a condition for forming the first hard coating, the pulsed bias voltage application is negatively and positively amplituded and strongly oriented on the (111) plane, thereby realizing high wear resistance of the first hard coating. it can. For this purpose, the bias voltage application can be realized by making the amplitude between negative 100 to 200V and positive voltage 5 to 10V.

  In order to make the Is / Ir value of the first hard film 0.2 ≦ Is / Ir ≦ 1.4, it is necessary to control the bias voltage, and it is preferable to apply the bias voltage in a pulsed manner. When the bias voltage is less than minus 100 V, the Is / Ir value tends to increase and the compressive stress is reduced, but the hardness of the first hard film is lowered and the wear resistance is deteriorated. When film formation is performed by applying a relatively high negative bias voltage up to minus 200 V, the kinetic energy of ions attracted to the substrate increases. That leads to an increase in compressive stress. The compressive stress is also affected by the film thickness of the first hard coating. That is, the thicker the film, the more the compressive stress tends to increase. The first hard film having a face-centered cubic structure according to the present invention was strongly oriented to the (111) plane that is the most filled surface of atoms to form a thick film. However, when the thickness of the first hard coating is increased, the compressive stress is remarkably increased and high adhesion to the substrate cannot be obtained. Therefore, it is necessary to adjust the kinetic energy when the element constituting the first hard film ionized in the plasma at the time of film formation reaches the substrate by applying a pulsed bias voltage. The control of the pulse frequency is particularly important when the bias voltage is pulsed. When the bias voltage is applied in the form of a pulse, it becomes possible to change the peak intensity of the (111) plane, the (200) plane, and the (220) plane, and at this time, particularly suppresses crystal growth on the (200) plane. By doing so, it becomes possible to improve wear resistance while ensuring high adhesion. It is considered that the structure of the first hard coating slips on the (111) plane and the compressive stress is relieved.

  When the pulse frequency is 5 to 35 kHz, the It / Is value is 0.6 ≦ It / Is ≦ 1.5, and the compressive stress of the first hard coating at this time is in an optimal range of 2.0 to 6.0 GPa. Can be. When the pulse frequency is lower than 5 kHz, the It / Is value exceeds 1.5. If it exceeds 35 kHz, the kinetic energy when ions reach the substrate cannot be adjusted, so the It / Is value is less than 0.6.

  If the bias voltage applied when forming the second hard film is pulsed in the same manner as the conditions for forming the first hard film, the kinetic energy of boron (B) ions reaching the substrate can be adjusted. Incorporated into the crystal lattice of titanium nitride (typically referred to as TiN), the second hard coating has a single crystallized structure containing B.

  As a condition for forming the second hard coating, the compression stress of the second hard coating is controlled by amplifying the pulsed bias voltage application to negative and positive and strongly orienting the (200) plane. Can do. For this purpose, bias voltage application can be realized by amplifying the negative voltage between 20 and 100 V, the pulse frequency between 5 and 35 kHz, and the positive voltage between 5 and 10 V. At this time, in the X-ray diffraction of the second hard film, when the peak intensity Iu of the (111) plane, the peak intensity Iv of the (200) plane, and the peak intensity Iw of the (220) plane are 5.0 ≦ Iv / Iu ≦ 15.0 and 2.0 ≦ Iw / Iu ≦ 4.0. When the second hard film is controlled within the above range, the toughness of the hard film is increased and the impact resistance is excellent. Furthermore, the wear resistance is improved. In addition to controlling the bias voltage, it is possible to control the reaction pressure in the range of 2 to 5 Pa. When the bias voltage at the time of forming the second hard film is less than 20 V, the peak of the (200) plane appears strongly, but the kinetic energy when ions reach the substrate decreases, and impurities are present at the grain boundaries during crystal growth. A large amount is taken in, the joint strength of the grain boundary is deteriorated, and the mechanical strength of the hard coating is inferior. Moreover, when it exceeds 100V, the residual compressive stress of a hard film will increase and adhesiveness with a 1st hard film will deteriorate.

  In order to set the Iv / Iu value of the second hard coating to 5.0 ≦ Iv / Iu ≦ 15.0, it is necessary to control the bias voltage, and it is preferable to apply the bias voltage in a pulsed manner. When the bias voltage is less than minus 20 V, the Iv / Iu value tends to increase and the compressive stress is reduced, but the hardness of the second hard film is reduced, the wear resistance is deteriorated, and the grain boundary is bonded. Strength deteriorates. When film formation is performed by applying a relatively high negative bias voltage exceeding minus 100 V, the kinetic energy of ions attracted to the substrate increases. That leads to an increase in compressive stress. By applying the bias voltage in a pulsed manner, it is necessary to adjust the kinetic energy when the element constituting the second hard coating ionized in the plasma during film formation reaches the substrate. The control of the pulse frequency is particularly important when the bias voltage is pulsed. When the bias voltage is applied in a pulsed manner, the peak intensity of the (111) plane, the (200) plane, and the (220) plane can be changed, particularly by suppressing crystal growth on the (111) plane. , Compressive stress can be suppressed and adhesion can be enhanced.

  When the pulse frequency is 5 to 35 kHz, the Iw / Iv value is 2.0 ≦ Iw / Iu ≦ 4.0, and the compressive stress of the second hard film at this time is set to an optimal range of 1 to 5 GPa. it can. When the pulse frequency is less than 5 kHz, the Iw / Iv value exceeds 4.0. On the other hand, if it exceeds 35 kHz, the kinetic energy when ions reach the substrate increases, and the peak on the (111) plane increases, so the Iw / Iv value becomes less than 2.0.

  On the other hand, when the second hard film is formed by applying only a DC bias voltage, B is replaced by a lattice of a face-centered cubic structure of TiN, cubic boron nitride (c-BN), hexagonal Crystalline boron nitride (h-BN), amorphous BN, and the like are often included in the second hard film. Since ions of B in the plasma are lighter elements than Ti and the like, it is considered that the ions reach the substrate with high kinetic energy and various unstable bonds are generated. When only the h-BN is included in the second hard coating, it is expected that the lubrication characteristics are improved and the rake face wear can be suppressed, but it is difficult to contain h-BN alone. Since it comes to coexist with compounds having other crystal structures such as c-BN, the compressive stress increases. In particular, when a large amount of c-BN is contained, although it is possible to increase the hardness of the second hard coating, it is not preferable because the compressive stress increases and the adhesion deteriorates.

  Next, an important (111) plane peak intensity condition among the constituent features of the present invention will be described. A major feature of the present invention is that the first hard film having a face-centered cubic structure is most strongly oriented in the (111) plane when evaluated by X-ray diffraction. Due to this feature, in the present invention, the first hard film has a high hardness, and the durability against the cutting force from the shear direction in cutting is excellent.

  Generally speaking, the hard coating is destroyed (hereinafter referred to as a crack) in response to an external impact caused by cutting. The crack propagates through the grain boundary of the structure in the hard film in a direction perpendicular to the base, reaches the base, and causes cracks and wear. Therefore, when the orientation to the (200) plane in the first hard film in contact with the base becomes strong, the compressive stress is reduced and the adhesion of the first hard film is increased. However, the strong orientation to the (200) plane causes a problem that cracks are easily propagated due to deterioration of wear resistance due to a decrease in hardness and coarsening of the columnar structure, resulting in a disadvantage that the fracture resistance is lowered. The hard film coated tool of the present invention has excellent wear resistance by improving the mechanical properties of the second hard film, as well as improving the mechanical properties of the second hard film, as well as wear resistance in the first hard film. It is realized.

  As in the present invention, by strongly orienting the first hard film on the (111) plane, the propagation of cracks generated in the direction perpendicular to the substrate is reduced, and the wear resistance is increased. Therefore, in the present invention, in the X-ray diffraction of the first hard film, when the peak intensity of the (111) plane is Ir, the peak intensity of the (200) plane is Is, and the peak intensity of the (220) plane is It, The Is / Ir value of the hard coating is defined as 0.2 ≦ Is / Ir ≦ 1.4, and the It / Is value is defined as 0.6 ≦ It / Is ≦ 1.5. If the first hard coating is 0.2 ≦ Is / Ir ≦ 1.4, excellent wear resistance can be realized, and if 0.6 ≦ It / Is ≦ 1.5, proper compression is achieved. A range of stress can be obtained. Accordingly, the first hard film having high hardness can be obtained while the thick film has high adhesion. However, when the Is / Ir value is less than 0.2 and the It / Is value is less than 0.6, the cross-sectional structure of the first hard coating is remarkably refined and the compressive stress increases. Therefore, although abrasion resistance is excellent, film peeling occurs easily. In particular, when the It / Is value is less than 0.6, the internal defects of the first hard coating are remarkably increased. When the It / Is value is less than 0.6, the compressive stress of the first hard film can be controlled even if the Is / Ir value is 0.2 ≦ Is / Ir ≦ 1.4. It becomes difficult. At this time, the compressive stress of the first hard film is about 6.5 GPa, and the adhesion between the substrate and the first hard film is remarkably deteriorated. Therefore, it is defined as 0.6 ≦ It / Is ≦ 1.5. When the Is / Ir value is larger than 1.4 and the It / Is value is larger than 1.5, the compressive stress is reduced and the adhesion is increased. However, on the other hand, the hardness is significantly reduced and the wear resistance is poor. Moreover, the joint strength at the grain boundaries in the cross-sectional structure of the hard coating is reduced, and the fracture resistance is deteriorated.

  With respect to the second hard film, when X-ray diffraction of the hard film is defined as (111) plane peak intensity Iu, (200) plane peak intensity Iv, and (220) plane peak intensity Iw, 5.0 ≦ Iv / It is specified in the ranges of Iu ≦ 15 and 2.0 ≦ Iw / Iu ≦ 4.0. As a condition for forming the second hard coating, the compression stress of the second hard coating is controlled by amplifying the pulsed bias voltage application to negative and positive and strongly orienting the (200) plane. And impact resistance is improved. For this purpose, bias voltage application can be realized by amplifying the negative voltage between 20 and 100 V, the pulse frequency between 5 and 35 kHz, and the positive voltage between 5 and 10 V. Controlling the second hard film within the above range increases the hardness of the hard film and improves the wear resistance. In addition to controlling the bias voltage, it is possible to control the reaction pressure in the range of 2 to 5 Pa. When the bias voltage at the time of forming the second hard film is less than 20 V, the peak of (200) appears strongly, and the impact resistance and wear resistance are inferior. Moreover, at 100 V or more, the residual compressive stress of the hard coating increases, and the adhesion with the first hard coating deteriorates.

  In the hard coating according to the present invention, 1.01 ≦ d2 / d1 when the distance (nm) between the (111) planes in the X-ray diffraction of the first hard coating and the second hard coating is d1 and d2, respectively. ≦ 1.05 and by setting d2 / d1 value to 1.01 ≦ d2 / d1 ≦ 1.05, the adhesion between the first hard film and the second hard film is improved, and the wear resistance is improved. Excellent. In order to improve the adhesion between the hard films, it is necessary to reduce the crystal lattice strain. In order to reduce this distortion, high adhesion can be obtained by reducing the difference in (111) plane spacing between hard coatings to reduce misfit. Therefore, by defining the d2 / d1 value in a range of 1.01 ≦ d2 / d1 ≦ 1.05, a hard coating having excellent wear resistance can be obtained without impairing adhesion to the substrate. If the d2 / d1 value is less than 1.01, the compressive stress of the entire hard coating increases, and the adhesion to the substrate deteriorates. If it exceeds 1.05, the number of internal defects at the film interface increases, and not only the adhesion is impaired, but also the compressive stress increases and the adhesion with the substrate decreases. As an example of the film forming condition, the method of setting the range of 1.01 ≦ d2 / d1 ≦ 1.05 is to use the pulse frequency in bias application as the film forming condition in the range of 5 kHz to 35 kHz.

  Regarding the hard film according to the present invention, the second hard film has a columnar structure, the crystal grains have a compositional modulation structure of the B component without forming an interface in the growth direction, and the layers having a compositional difference in the B component Crystal lattice fringes continuously grow in the boundary region. Here, the columnar structure is a vertically grown crystal structure extending in the film thickness direction. The second hard film is a polycrystalline material, but has a form similar to the growth of a single crystal material when grasped in units of crystal grains. As a feature of the present invention, the crystal grains of the columnar structure of the second hard film include a B-enriched layer in which the content of the B component is relatively large with respect to the growth direction and a B-poority that is relatively small. The layers are alternately present and have a composition modulation structure having a composition difference of the B component. At this time, it is preferable that crystal lattice fringes are continuous at the composition modulation boundary in the composition modulation structure. The second hard film has a B component composition modulation structure, and the mechanical strength is increased by controlling the compressive stress. For example, a B layer enriched layer forms a relatively soft layer. When this soft layer is present between other relatively hard layers, it exhibits a buffering effect, and the second hard coating as a whole relaxes the compressive stress and has toughness. Furthermore, the 2nd hard film | membrane which has lubricity can be obtained with the lubrication characteristic of B component. However, the preferable composition difference of the B component at this time is 10% at the maximum. More preferably, it is in the range of 0.1% or more and 7% or less.

  In order to obtain a composition-modulated structure of the B component, for example, a target material having a different B content is used, such as a combination of a target material having a relatively large B content and a target material having a relatively small composition. This can be realized by performing film formation while applying a pulse bias. The second hard coating according to the present invention can be realized by applying a high bias voltage by a pulse bias. Therefore, in particular, in the second hard coating, since B having an ion radius smaller than that of Ti is contained in the crystal lattice of the face-centered cubic structure TiN, it is necessary to control the kinetic energy of ions by applying a pulse bias. By applying a pulse bias, the portion where the B content in the columnar structure has a compositional difference has a structure in which the B component is alternately modulated, and crystal lattice fringes are continuous between the B-rich layer and the B-poor layer. And grow up. On the other hand, when a high DC bias voltage is applied, it becomes difficult to contain B in the second hard film. The composition modulation structure in which the crystal lattice fringes between the layers are continuously grown has an acceleration voltage of 20 kV using, for example, a JEM-2010F type field emission transmission electron microscope (hereinafter referred to as TEM) manufactured by JEOL Ltd. This can be confirmed by observing the columnar structure under conditions.

  By setting the film thickness of the entire hard coating to 5 μm or more, excellent wear resistance can be obtained. On the other hand, if it exceeds 30 μm, the hard coating film has a high compressive stress and deteriorates the adhesion to the substrate, so that it is preferably 30 μm or less. Further, the film thickness of the first hard film is thicker than that of the second hard film, and more preferably, the film thickness of the second hard film is 50% or less with respect to the film thickness of the entire hard film. The more preferable film thickness of the entire hard coating is 10 μm to 30 μm, whereby excellent wear resistance can be obtained.

Regarding the nitrogen element of the non-metallic component in the first hard film, when a part of the nitrogen element is replaced with a carbon element and an oxygen element, the content of the carbon element is x value and the oxygen element content is y value in atomic%. It is preferable that 0 <x ≦ 10, 0 <y ≦ 10, and 0 <x + y ≦ 10. Thereby, the 1st hard film which has high hardness, the outstanding oxidation-resistant characteristic, adhesiveness, and a lubrication characteristic is obtained. When carbon element and oxygen element are contained, in order to avoid mechanical strength deterioration, the sum of x value and y value is made 10% or less, so that excellent welding resistance and sliding property are obtained. More preferably, when the carbon element is contained alone, the content is 2% to 10%. However, when the x value and y value exceed 10%, the crystal structure becomes finer, and defects at the grain boundaries increase. As a result, even if the lubrication characteristics of the first hard coating are improved, the compressive stress increases, and thus a defect that adhesion and fracture resistance are lowered appears. When the first hard film contains a carbon element or an oxygen element, it is preferable to use a hydrocarbon-based gas or an oxygen-containing gas. When film formation is performed by introducing gas, the total pressure combined with nitrogen gas is preferably in the range of 3 to 8 Pa. When film formation is performed by introducing a gas in addition of carbon element, it is preferable to use nitrogen (N ₂ ), methane (CH ₄ ), acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₆ ), or the like. Easy to control. In the case of introducing a hydrocarbon gas, up to about 20% of the nitrogen flow rate is a range in which film formation can be performed stably. In the case of introducing oxygen gas, it is preferable to perform film formation by introducing nitrogen gas and oxygen gas, or nitrogen gas, oxygen gas, and argon. Alternatively, the target evaporation source can be contained as a compound containing a carbon element or an oxygen element.

  With respect to the Ti element of the metal component in the second hard film, when 1 part of the Ti element is substituted with the Si element and the entire metal component is 1, the content of Si element in atomic% is k, and 0 <k ≦ By setting it to 20, the wear resistance is improved. In order to make the second hard film a columnar structure, the k value is preferably 20% or less. When Si is contained, the second hard film having excellent wear resistance on the rake face of the cutting tool can be obtained, for example, by forming a single crystal of TiN into a solid solution. On the other hand, if the k value exceeds 20%, the structure becomes finer, the compressive stress increases, and the disadvantage of decreasing the adhesion appears. In addition, the second hard coating includes various structures in the form of TiN crystalline, SiN composition crystalline, or amorphous. As a result, crystal grain boundaries increase, crystal lattice distortion occurs, and compressive stress increases.

  The composition of the hard film of the present invention can be measured, for example, using a JXA8500F type EPMA analyzer manufactured by JEOL. Specifically, in the vertical cross section of the hard film or the inclined cross section obtained by inclining the film cross section at an angle of 17 degrees, the hard film is applied from a position not affected by the substrate, the acceleration voltage is 10 kV, the irradiation current is 1.0 μA, the probe diameter. The composition can be specified by setting the value to about 10 μm. When measuring from the surface of the hard coating, the probe diameter is preferably set to about 50 μm. Further, when carbon or oxygen is contained, if it is less than 2%, detection by analysis becomes difficult. The film thickness of the hard coating can be measured, for example, by observing the fracture surface in the vertical direction at a magnification of 25,000 times, for example, using an S-4200 type electrolytic emission scanning electron microscope manufactured by Hitachi, Ltd.

  The measurement of the peak intensity ratio of the (111), (200), (220) planes in the X-ray diffraction of the first and second hard coatings is, for example, 2θ using a RU-200BH type X-ray diffractometer manufactured by Rigaku Corporation. It can be measured by the -θ scanning method. In the embodiment of the present invention, the range of 2θ (degrees) is 10 to 145 degrees, the X-ray source is CuKα1 line having a λ value of 0.15405 nm, and background noise is removed by software built in the apparatus. As a result of the measurement, the detected 2θ peak position substantially coincided with the X-ray diffraction pattern (JCPDS file number 38-1420) of TiN whose crystal structure is a face-centered cubic structure. , (220) peak intensity was measured. For the peak intensity, the maximum value of the peak top on each index plane was taken as the peak intensity, and the peak intensity ratio was determined using this. Furthermore, the numerical value of the peak position which shows the said (111) plane was applied to the surface space | interval. Further, the peak intensity was measured in the same manner for the first hard coating based on CrN.

  The compressive stress in the hard film according to the present invention can be calculated by the following curvature measurement method. That is, when a test piece obtained by processing a substrate having a known Young's modulus and Poisson's ratio into a predetermined shape is coated on the surface, the coated test piece is caused by the compressive stress generated in the hard film. Deforms and deforms. The amount of deflection deformation is obtained, and the numerical value 1 is used to calculate the compressive stress σ value of the entire hard coating. In Examples and the like described later, numerical values calculated by this method are described.

  Here, the Es value (GPa) is the Young's modulus of the substrate used for the test piece, the D value (mm) is the thickness of the test piece, the δ value (μm) is the amount of deflection of the test piece before and after coating, and the l value ( mm) is the length from the end surface in the longitudinal direction of the test piece where the deflection is caused by the coating to the maximum deflection part, νs value is the Poisson's ratio of the substrate used for the test piece, and d (μm) is coated on the surface of the test piece. It is the film thickness of the hard coating. In addition, as a material for forming the test piece, a cemented carbide material is suitable with little variation in measured numerical values. The shape of the test piece is preferably a strip shape. For example, when a shape having a width of 8 mm, a length of 25 mm, and a thickness of 0.5 to 1.5 mm is used, variation in measured numerical values is small. The upper and lower surfaces having a large area of the test piece are mirror-polished so that the parallelism is ± 0.1 mm, and then heat-treated in a vacuum of 600 to 1000 ° C., and particularly the surface portion of the material used for the test piece. It is important to remove the distortion. Unless this strain is removed to some extent, the resulting compressive stress values will vary. After measuring the deflection deformation amount of one mirror-finished surface having a large test piece area before coating, the surface is coated, and the deflection amount of the obtained coated test piece is measured again. Measure the amount of deflection before and after coating, the length from the end face in the length direction of the test piece where the deflection occurred to the maximum deflection, and the film thickness of the coated hard coating. For example, it is possible to calculate the value of the compressive stress even if the composition of the hard film and the film forming conditions are changed or the composition has a modulation structure.

  When the hard coating tool is made of tungsten carbide base cemented carbide, high speed tool steel, cermet or the like as the substrate, the balance between wear resistance and toughness is further optimized. However, when high-speed tool steel is used as the substrate, it is preferable to coat by physical vapor deposition in the range of 500 to 550 ° C. in consideration of its heat treatment characteristics. When the film is formed at such a relatively low temperature, the bias voltage to be applied and the reaction pressure at the time of film formation are appropriately optimized. As a film forming method, a film forming method in which a pulsed bias voltage can be applied and compressive stress is applied is preferable. An ion plating method such as an arc ion plating (hereinafter referred to as AIP) method or a sputtering method is preferred. If appropriate manufacturing conditions are applied, a composite apparatus in which each method is installed in one facility may be used. The present invention will be described in more detail by the following examples, but the present invention is not limited thereby.

  A hard coating according to the present invention was coated on a surface of a cemented carbide substrate having a test piece capable of measuring compressive stress and a turning insert shape, thereby producing a sample of the present invention example 1. In Example 1 of the present invention, an AIP apparatus was used, and the target material 1 having a metal component composition of atomic%, Ti: 50%, and Al: 50% was used. A (TiAl) N film having a composition of only the metal component and containing Ti: 50% and Al: 50% was formed as a first hard film so as to have a film thickness of 6 μm. Then, the 2nd hard film was formed into a film using two types of target materials from which B content differs. That is, the target material 2 with the composition of the metal component of atomic percent, Ti: 86% and B: 14%, and the target material 3 with Ti: 84% and B: 16% were used. A (TiB) N film having a composition of only metal components of Ti: 85% and B: 15% was formed as a second hard film with a film thickness of 6 μm, and the total film thickness was 12 μm. Thus, in the film formation of the second hard coating, the turning insert is placed between the target material 2 and the target material 3 by the jig loaded with the turning insert performing a planetary motion in the AIP apparatus. The crystal grains in the columnar structure were adjusted so as to have a B-component composition modulation structure by alternately approaching and leaving when passing through. The film formation temperature was set to 550 ° C., the reaction pressure was set to 3.5 Pa, and nitrogen gas was introduced during film formation in order to form nitrides. The (TiAl) N film, which is the first hard film, is formed by forming a 1 μm film with a negative bias voltage of 150 VDC and then applying a pulsed bias voltage. The pulse frequency was set to 10 kHz, and the positive bias voltage was set to 5V. After forming the (TiAl) N film, a (TiB) N film as the second hard film is formed to a thickness of 1 μm with a negative bias voltage of DC 50V, and then a pulsed bias voltage is applied. The film was formed under the conditions of a pulse frequency of 10 kHz and a positive bias voltage of 5V. The evaporation source is selected from various alloy targets according to the present invention and the comparative example, and in order to obtain nitrides, carbonitrides, oxynitrides, oxycarbonitrides, nitrogen, oxygen, methane, etc. A hydrocarbon-based gas was produced either alone or mixed and introduced during film formation. Inventive Examples 2 to 42 and Comparative Examples 43 to 63 in which the film thickness, composition, X-ray diffraction peak intensity, and compressive stress of the hard coating were changed using the film forming conditions of Inventive Example 1 as a standard were prepared. .

  Tables 1, 2, 3, and 4 show details of the prepared samples, hard coating composition, manufacturing conditions of the hard coating, measured values of compressive stress, and evaluation results of the cutting test of the coated insert. Further, as a result of observation of the film cross-section by TEM, the second hard film in the example of the present invention all has a columnar structure, and the crystal grains of this columnar structure have a compositional difference in the B component with respect to the crystal grain growth direction. It was confirmed that it has. For example, the second hard coating of Invention Example 1 has a columnar structure as a result of observation of the cross section of the coating by TEM, and the crystal grains have a composition modulation structure having a composition difference in the B component with respect to the growth direction. This is because the composition difference of the B component between the B-enriched layer and the B-poor layer was 2% because the second hard film was formed using target materials having different B contents. Further, crystal lattice stripes were continuously grown between the layers. On the other hand, some of the comparative examples had a composition modulation structure having a composition difference in the B component. However, a small composition difference showed a high compressive stress.

  The produced turning insert was attached to a blade-type replaceable cutting tool, and a turning test was performed under the following conditions to confirm superiority or inferiority of wear resistance, fracture resistance, and adhesion. The insert used for the cutting evaluation uses a general-purpose CNMG120408 shape, using cemented carbide as a base, and HRA91 corresponding to M20 type in the JIS standard. In turning, a special insert with a chip breaker and a rake angle of 3 degrees was used. In the evaluation method, the abrasion generated on the flank and rake face of the hard film-coated insert generated at a cutting distance of 5 m was observed with an optical microscope at a magnification of 50 times. Further, when cutting was continued and a defect including micro chipping of 10 μm or more occurred, or when there was no defect, the tool life was defined as the time when the VBmax value of the flank wear width reached 0.3 mm, and the cutting distance at this time The performance was evaluated by (m). The damage state of the cutting edge during cutting was appropriately observed.

(Cutting test conditions)
Cutting method: Continuous cutting in the longitudinal direction Work material shape: Round bar material with a diameter of 160 mm and a length of 600 mm Work material: S53C, HB260, tempered material Axial depth of cut: 2.0 mm
Cutting speed: 300 m / min Feed rate per rotation: 0.4 mm / rotation Cutting oil: None

  Invention Examples 1 to 5 and Comparative Examples 43 and 44 were prepared in order to see the influence of the film thickness of the hard coating. The film thickness was adjusted by the coating time. The film thickness ratio of the first hard film and the second hard film was the same as 1: 1, and only the entire film thickness was changed. The compressive stress tended to increase as the thickness of the hard coating increased. Those having a total film thickness of 5 μm or more shown in Invention Examples 1 to 5 were excellent in wear resistance such as flank wear and crater wear. In any of the samples, there was no occurrence of welding of the workpiece component to the cutting edge in the initial 5 m of cutting. It was thought that these had the big effect with respect to crater abrasion and welding resistance to have the 2nd hard film prescribed | regulated by this invention. In Example 1 of the present invention, the total film thickness was 12 μm, the compressive stress value was 2.4 GPa, and a satisfactory tool life of 16 m was obtained. As a result of confirming the damage state of the cutting edge when the cutting distance is 5 m, the flank wear amount is 0.041 mm, which is superior in wear resistance than the present invention examples 4 and 5 having a thin film thickness. Compared to Comparative Example 44, the tool life was 8 times or more. When the damaged state of the cutting edge was confirmed during cutting, the hard coating was not dropped, peeled off, chipped, or the like in the vicinity of the cutting edge, and normal wear was exhibited. The example of the present invention in which film formation was performed by applying a pulsed bias voltage had a long tool life and excellent results.

  The total film thickness of Comparative Example 43 was 40 μm, the compressive stress was 7.1 GPa, and the tool life was inferior to Invention Examples 1-5. In Comparative Example 43, fine film breakage was observed at the edge of the blade edge before cutting. When the damage state of the edge part of the cutting edge during the cutting was confirmed, the film breakage expanded to a width of 9 μm, and the breakage part led to a defect. This is because the compressive stress is increased by increasing the total film thickness to 40 μm. The total film thickness of Comparative Example 44 was 4 μm and had a low compressive stress of 1.3 GPa. However, although the abrasive wear was inferior, there was little peeling of the hard coating, but the tool life was short.

  Invention Examples 6 and 7 were prepared in order to observe the influence of the film thickness ratio of the first hard film and the second hard film. As shown in Inventive Example 6, the tool life was superior to Inventive Example 1 by increasing the thickness of the first hard coating. This was considered to be because progress of flank wear was suppressed. However, in Invention Examples 6 and 7, the second hard film was as thin as 1 μm and 3 μm, respectively, and crater wear occurred during cutting. As the crater wear progresses to the base material, the strength of the blade edge is lost, leading to defects. In order to confirm reproducibility, cutting evaluation was also performed for a film having a total film thickness of 12 μm and a second hard film coated to 0.3 μm, but the progress of flank wear was suppressed, but crater wear was the main component. Progressed to life.

  Invention Examples 8 to 20 and Comparative Examples 45 and 46 were prepared in order to observe the influence of the composition of the first hard coating. It was produced by changing the composition of the target material for coating. Invention Example 10, which has the best tool life, contained 10% tungsten (W), and was about 1.5 times better than Invention Example 1. When the cutting edge state was confirmed when the cutting distance was 5 m, chipping was not confirmed at the cutting edge part, and the flank wear was 0.027 mm. There was almost no welding of the workpiece at the cutting site, and the life was reached only by the progress of normal wear. It is considered that the reason why the flank wear is excellent is that the hardness is increased by containing W. The hardness of the first hard coating in Invention Example 1 was 28 GPa, and Invention Example 10 was 31 GPa. Furthermore, since the oxidation resistance has increased, it is considered that the progress of flank wear was suppressed. In particular, when the oxidation resistance is increased, damage at the tool boundary where the cutting heat is highest tends to be reduced. Further, the reason why welding did not occur is that boron (B) was contained in the second hard film of the outermost film and the lubrication characteristics were excellent. The contained B exists as a BN crystal in the second hard film, and partly dissolved in the TiN crystal lattice undergoes spinodal decomposition to form a relatively soft B oxide on the hard film outermost surface. It is to do. Invention Example 12 contains 10% of niobium (Nb), and Invention Examples 13 and 14 contain chromium (Cr) and silicon (Si), so that the mechanical properties of the first hard coating are enhanced, and Invention Example 1 Excellent compared to As shown in Invention Example 15, the tool life was excellent even when B was contained in the first hard coating. Welding was also suppressed at the portion of the first hard film exposed after the second hard film was worn. Even when B was contained in the first hard film, a remarkable effect was obtained with respect to welding and crater wear. In Invention Examples 8 to 20, since the first hard film is a nitride of an element selected from Al, Group 4a, 5a, and 6a elements, Si, and B, heat resistance and hardness are remarkably improved. In addition to the examples of the present invention, wear resistance tends to be excellent due to the combination of the above elements. In the (AlCr) N-based hard coatings shown in Invention Examples 16 to 18, crater wear appeared earlier than the (TiAl) N-based hard coatings. However, the wear progress at the boundary tends to be slow and the tool life is excellent. It was considered that the (AlCr) N-based hard coating had better oxidation resistance than the (TiAl) N-based hard coating.

  In Comparative Example 45, the Al content of the first hard coating was 75%, and the welding phenomenon and the abrasive wear of the tool flank progressed from the beginning of cutting. In the observation of the structure of the first hard film cross section, the structure was refined. For this reason, compressive stress increases and adhesion deterioration can be considered. Further, the hardness of the first hard film was 18 GPa, and the decrease in hardness caused early progress of wear. As a result of performing X-ray diffraction on Comparative Example 45, a hexagonal structure peak appeared in addition to the face-centered cubic structure peak. As a result of the investigation, it was confirmed that the peak was attributed to the AlN compound. Thereby, it is considered that the wear resistance is remarkably deteriorated. In Comparative Example 46, the same phenomenon was confirmed. Al content has the effect of increasing the oxidation resistance of the hard coating, and reduces damage at the boundary in cutting. The hard coating tool of the present invention was investigated for the optimal Al content including reproducibility confirmation, but when the Al content exceeds 65 atomic% with only the metal component, the wear resistance deteriorates, and when it becomes 75%, The wear resistance deteriorated rapidly. Further, in Comparative Example 45, Is / Ir was 1.88, and the peak intensity of the (200) plane of the first hard coating was increased. The deterioration of the wear resistance is considered to be caused not only by the appearance of the hexagonal structure peak, but also by the excessive increase in the peak intensity on the (200) plane. As a result of observation of the cross section of the second hard film by TEM for Comparative Examples 45 and 46, the result was a columnar structure, and the crystal grains had a composition modulation structure having a composition difference in the B component with respect to the growth direction. However, the difference in composition of the B component was small, and both Inventive Examples 45 and 46 were less than 0.1%. Further, crystal lattice stripes were continuously grown between the layers.

  Invention Examples 21 to 24 and Comparative Examples 47 and 48 were prepared in order to see the influence of the composition of the second hard film. It was produced by changing the composition of the target material for coating. In inventive examples 21 and 22, the B content of the second hard coating was 1% and 25%, respectively. Invention Examples 23 and 24 contained B and Si. As a result of film cross-sectional observation of these second hard films by TEM, it was found that the crystal grains had a columnar structure and the crystal grains had a composition modulation structure having a composition difference in the B component with respect to the growth direction. By forming the second hard film using target materials having different B contents, the compositional difference of the B component was 0.5% for Invention Example 21 and 7% for Invention Example 22, respectively. 23 was 0.1% and Invention Example 24 was 4%. Further, crystal lattice stripes were continuously grown between the layers. On the other hand, regarding Comparative Example 47 in which the B content of the second hard coating is 40% and Comparative Example 48 in which the Si content is 30%, the cross-sectional structure of the second hard coating is observed, and both are refined structures. It was confirmed. When the B and Si contents were increased, peeling of the hard coating and crater wear occurred from the beginning of cutting. The difference in the film structure resulted in superiority or inferior cutting performance. In particular, in Comparative Example 48 in which the Si content was 30%, many deposits were observed on the surface of the second hard film from the middle of cutting. Moreover, it was thought that peeling of the hard film was caused by an increase in residual compressive stress. When B and Si are contained alone, those with a B content in the range of 1 to 25%, and those with a Si content up to 20% are reproducible and exhibit excellent wear resistance. . As a result of various studies on the case where both B and Si are contained, the second hard coating tends to have excellent wear resistance in the region of B + Si ≦ 25%.

  Invention Examples 25 and 26 and Comparative Examples 49 and 50 were prepared in order to observe the influence of oxygen element and carbon element contained in the first hard film. Oxygen and hydrocarbon gas were used as part of the reaction gas. For Invention Example 26 and Comparative Example 50 containing oxygen, nitrogen, argon (Ar), and oxygen were simultaneously introduced during film formation. In all cases, the total pressure was set to 3.0 Pa. In the case of Invention Example 26, the gas was introduced at a gas flow ratio of 85% nitrogen: 10% argon: 5% oxygen. In this case, when a large amount of oxygen was introduced, the arc discharge generated during film formation became unstable. Therefore, the inert gas Ar was introduced to adjust the total pressure. Although discharge is possible without using Ar gas, Ar gas was introduced for further stabilization. In Comparative Example 50, in order to increase the oxygen content, the amount of nitrogen was reduced while the total pressure was 3.0 Pa, and the amounts of Ar gas and oxygen gas were increased. The tool life of Inventive Examples 25 and 26 was about 1.4 times better than Inventive Example 1 that did not contain oxygen and carbon elements. Moreover, the damage state of the blade edge at the time of the cutting distance of 5 m tended to be less welded and flank wear than the first example of the present invention. Furthermore, the occurrence of crater wear on the rake face was reduced. Crater wear occurs due to a chemical reaction accompanying an increase in cutting temperature, so that the inclusion of oxygen and carbon elements increases the lubrication characteristics and reduces the friction coefficient. As a result, it is considered that the cutting temperature at which the chips scrape the rake face is suppressed, and wear is reduced.

  In Comparative Examples 49 and 50, since the x value and y value of the first hard film were 10% or more, peeling of the hard film and occurrence of crater wear were confirmed from the beginning of cutting, and the structure observation of the cross section of the first hard film was similarly performed. As a result, it was miniaturized. For Invention Example 1 containing no carbon element, Invention Example 25 having a carbon content of 7%, and Comparative Example 49 having a carbon content of 15%, a sample of only the first hard film was prepared and the coefficient of friction was measured. The coefficient of friction was measured by a ball-on-disk method, and a SUJ2 φ6 mm ball was slid on a coated cemented carbide disc and measured without lubrication in the atmosphere. The wear resistance and welding resistance of the hard film at a measurement temperature of 600 ° C. were investigated. The friction coefficient of Invention Example 1 was 0.8, Invention Example 25 was 0.45, and Comparative Example 49 was 0.8. Even if the first hard coating contains a large amount of carbon element, it is confirmed that damage such as flank wear, crater wear and welding of the work piece to the tool edge will occur from the beginning of cutting if the structure of the cross section of the coating becomes finer. It was done. The same tendency was observed when oxygen was contained. When a large amount of oxygen or carbon was contained, the hardness of the hard film was 16 GPa, which was lower than Example 1 of the present invention. Furthermore, it was confirmed that when a large amount of carbon or oxygen is contained, the strain tends to increase at the interface between the first hard film and the second hard film. As a result of observation of the cross section of the second hard film by TEM for Comparative Examples 49 and 50, the result was a columnar structure, and the crystal grains had a composition modulation structure having a composition difference in the B component with respect to the growth direction. However, the difference in composition of the B component was small, and both Inventive Examples 49 and 50 were less than 0.1%. Further, crystal lattice stripes were continuously grown between the layers.

  Invention Examples 27 to 29 and Comparative Examples 51 and 52 were prepared in order to observe the influence of the reaction pressure on the composition during film formation. In particular, the influence of the e / f value on the compressive stress was investigated. At this time, the reaction pressure was changed and set in the range of 1.6 Pa to 13.5 Pa. In the case of Inventive Examples 1 and 27 to 29 in which the film was formed at a reaction pressure of 2.2 to 8.1 Pa, the tool life was excellent on the high pressure side as compared with Inventive Example 1. Invention Example 29, which is on the low pressure side as compared with Invention Example 1, has a far superior tool life as compared with Comparative Examples 51 and 52, but extremely minute chipping occurred at the beginning of cutting. In particular, Invention Example 27 having an e / f value of 1.07 was most excellent, and unstable elements such as chipping of the first hard coating did not occur. In Comparative Example 51 in which the film was formed at the lowest reaction pressure of 1.6 Pa, the compressive stress was 7.1 GPa, the e / f value was 0.82, and the tool life was 4 m. This was a life of about 25% as compared with Example 1 of the present invention. The lower the nitrogen pressure, the greater the compressive stress and the lower the e / f value. This reason is considered to be because the compressive stress of the first hard coating is high. When the compressive stress exceeded 6.0 GPa, it was confirmed that the first hard coating was broken at the edge of the blade edge in the damage state of the insert blade edge during cutting. In order to confirm reproducibility, as a result of cutting evaluation of several degrees using a new corner of the insert of Comparative Example 51, the tool life was 2 m and 0.2 m and was not stable.

  In Comparative Example 52, the compression stress was a relatively low value of 0.5 GPa, but the tool life was 3 m. Since the damage state of the cutting edge at the cutting distance of 5 m could not be observed, the damage at the initial cutting distance of 1 m was confirmed using a new corner, and as a result, the film from the substrate and the first hard coating interface at the edge of the cutting edge A large amount of welding occurred at the site where peeling and the first hard coating were removed. In addition, large wear on the flank and crater wear occurred. This was thought to be due to a decrease in the hardness of the first hard coating. The e / f value was 1.32. Although the cross-sectional structure of the first hard film had a columnar structure, many defects were generated in the first hard film, and the adhesion and wear resistance were poor. The reason for this is considered to be that the kinetic energy when ions are incident on the substrate is extremely low due to the reaction pressure being 13.5 Pa.

  Invention Examples 30 to 33 and Comparative Examples 53 and 54 were prepared in order to observe the influence of the Is / Ir value. During film formation, the pulse frequency of the pulse bias was kept constant at 10 kHz, and the bias voltage value was changed and set in the range of 100 to 300V. Invention Example 1 and Invention Examples 30 to 33 have an Is / Ir value within the specified range of the present invention, a compressive stress of 4 GPa or less, and an excellent tool life. Further, when the bias voltage was changed, the Is / Ir value was changed, and the compressive stress was changed accordingly. In Comparative Examples 53 and 54, the compressive stress exceeded 8 GPa, and delamination of the hard coating was observed from the beginning of cutting. When the compressive stress was increased, the tool life was inferior. As a result of observing the cross section of the second hard film with TEM in Comparative Examples 53 and 54, it was found that the crystal grains had a columnar structure and the crystal grains had a composition modulation structure having a composition difference in the B component in the growth direction. However, the difference in the composition of the B component was small, and both Invention Examples 53 and 54 were less than 0.1%. Further, crystal lattice stripes were continuously grown between the layers.

  Invention Examples 34 to 36 and Comparative Examples 55 to 57 were prepared in order to observe the effect of the It / Is value on the compressive stress. At this time, the positive bias value of the pulse bias voltage was changed from 10 to 40V. When the positive bias voltage increases, the orientation strength toward the (200) plane tends to be relatively strong, and the It / Is values of Invention Examples 1, 34 to 36, and Comparative Examples 55 to 57 are 0.21. It changed to ˜1.44. In Invention Example 1 and Invention Examples 34 to 36, the It / Is value was within the specified range of the present invention, the compressive stress was relatively low, and a satisfactory tool life was obtained. On the other hand, in Comparative Examples 55 to 57, the positive bias voltage exceeded 20 V, the It / Is value was less than 0.6, and in the blade edge damage observation at the cutting distance of 5 m, many peelings of the first hard film were observed. . Since the compressive stress increased and exceeded 6 GPa, not only peeling from the interface between the substrate and the first hard coating but also many shell-like fractures were observed, which resulted in a decrease in tool life. In order to improve the adhesion at the interface between the first hard film and the second hard film, the positive bias voltage value in the pulse bias voltage is controlled to be low, and the orientation strength of the (200) plane of the first hard film is lowered. This is very important. This is because application of a bias voltage having only a negative value is insufficient for suppressing defects caused by micro arcing during film formation. As a result of observation of the cross section of the second hard film by TEM in Comparative Examples 55 to 57, the result was a columnar structure, and the crystal grains had a composition modulation structure having a composition difference in the B component with respect to the growth direction. However, the difference in the composition of the B component was small, and both Inventive Examples 55 to 57 were less than 0.1%. Further, crystal lattice stripes were continuously grown between the layers.

  Inventive Examples 1, 37 and 38 and Comparative Examples 58 and 59 were produced by changing the bias voltage during film formation of the second hard film from 20 to 120 V in order to see the influence of the Iv / Iu value. In Invention Examples 1 and 37 to 38, the Iv / Iu value tended to increase when the bias voltage was lowered. Further, it was confirmed that when the bias voltage is higher than 100 V, the residual compressive stress tends to increase. Inventive Examples 1 and 37 to 38 were superior in tool life to Comparative Examples 58 and 59. In Comparative Example 58, the residual stress of the hard coating was 0.1 GPa. This was thought to be because the Iv / Iu value was 15.46 and the film was oriented strongly in the (200) plane, so that the hardness of the hard coating was reduced, which caused the flank wear to progress quickly. In Comparative Example 59, the residual compressive stress of the hard coating was 7.4 GPa as a result of coating with a bias voltage of 120V. In Comparative Example 59, it was observed that the hard coating dropped off on the blade edge before cutting. When further cutting was performed, film peeling was observed before the cutting distance was less than 2 m, and the site was deficient from that point. As a result of observing the cross-sectional structure of the hard coating, it was considered as a fine structure and increased grain boundary defects. This was considered to be the cause of the increase in residual compressive stress.

  Inventive Examples 1, 39 and 40 and Comparative Examples 60 and 61 were produced by changing the pulse frequency at the time of forming the second hard film to 2 to 40 kHz in order to see the influence of the Iw / Iv value. In Invention Examples 1, 39 and 40, the Iw / Iv value tended to decrease when the pulse frequency was increased. Further, it was confirmed that the residual compressive stress tends to increase when the pulse frequency is increased. Inventive Examples 1, 39, and 40 were superior in tool life to Comparative Examples 60 and 61. In Comparative Example 60 with a pulse frequency of 2 kHz, the residual compressive stress of the hard film showed a low value of 1.9 GPa, but the Iw / Iv value was 2.42. Although the cause is unknown, peeling was observed between the base and the first hard film, and between the first hard film and the second hard film from the beginning of cutting. In Comparative Example 60, the reproducibility of the cutting performance was confirmed with a plurality of samples, but all of them had a tool life shorter than that of Inventive Example 1. This is because the pulse frequency applied to the bias voltage at the time of film formation was 2 kHz, so the kinetic energy when ions reached the substrate was low, and it did not particularly deteriorate the adhesion of the hard coating. It is thought. In Comparative Example 61, since the pulse frequency was 40 kHz, the kinetic energy of ions could not be controlled, which was accumulated as strain during the formation of the hard film, and the residual compressive stress increased. For this reason, it is considered that the peeling of the hard coating may have occurred in the early stage of cutting.

  Invention Examples 41 and 42 and Comparative Examples 62 and 63 were prepared in order to observe the influence of the (200) plane spacing in the X-ray diffraction of the first hard film and the second hard film. The surface spacing was adjusted by changing the pulse frequency of the pulse bias voltage applied during the formation of the first hard film in the range of 1 to 40 kHz. Inventive examples 41 and 42 are cases where the pulse frequency is 30 kHz and 2 kHz, respectively, and the d2 / d1 value is 1.01 to 1.02, and the compressive stress of the entire hard coating is reduced, and the first hard coating is reduced. And excellent adhesion of the second hard film, and a satisfactory tool life was obtained. On the other hand, in Comparative Example 62 in which the pulse frequency of the first hard film was 1 kHz, the d2 / d1 value was 1.07, and the adhesion was caused by the gap between the first hard film and the second hard film. Deteriorated. This is probably because the residual compressive stress increased. In Comparative Example 63, more peeling was observed at the interface between the first hard film and the second hard film than at the initial stage of cutting than between the base and the hard film. This was the cause of the short tool life. The reason for this is that since the film was formed at 40 kHz, the d2 / d1 value was 0.99, the compressive stress of the entire hard film increased to 6.9 GPa, and in addition to the adhesion to the substrate, the first hard film and the first hard film This is because the adhesiveness deteriorated due to misfit of the spacing between the two hard coatings. It was also confirmed that the It / Is value changed with the change of the pulse frequency. The relationship between the pulse frequency and the compressive stress is considered to be correlated, and the compressive stress tends to increase as the pulse frequency increases. This is considered to be due to the fact that the DC bias voltage is applied as the pulse frequency increases.

  The hard film-coated tool of the present invention can be applied to, for example, general tools for metal processing that require wear resistance.

Claims (5)

In a hard film coated tool in which a hard film having a compressive stress is coated on a substrate with a cemented carbide alloy in a film thickness of 5 to 30 μm, the hard film is coated with the first hard film and the second hard film from the surface of the substrate, The outermost coating is coated with the second hard coating, and the first hard coating is represented by (Al _a Me _100-a ) _e N _f , where a represents atomic%, and e and f represent atomic ratios. 35 ≦ a ≦ 65, 0.90 ≦ e / f ≦ 1.15, Al is aluminum, Me is one or more elements selected from Group 4a, 5a, 6a, Si, B, N is It is nitrogen, and the second hard coating is represented by (Ti _100-h B _h ) _m N _p , where h is atomic%, m and p are atomic ratios, 1 ≦ h ≦ 30,. 90 ≦ m / p ≦ 1.15, Ti is titanium, B is boron, N is nitrogen, the first hard coating, 2 The crystal structure of the hard film is a face-centered cubic structure. In the X-ray diffraction of the first hard film, the peak intensity of the (111) plane is Ir, the peak intensity of the (200) plane is Is, and the peak of the (220) plane is When the intensity is It, 0.2 ≦ Is / Ir ≦ 1.4 and 0.6 ≦ It / Is ≦ 1.5, and the (111) plane in the X-ray diffraction of the second hard film 5 ≦ Iv / Iu ≦ 15 and 2 ≦ Iw / Iv ≦ 4 when the peak intensity Iu, the (200) plane peak intensity Iv, and the (220) plane peak intensity Iw, the first hard When the distance (nm) between the (111) planes in the X-ray diffraction of the coating and the second hard coating is d1 and d2, respectively, 1.01 ≦ d2 / d1 ≦ 1.05, and the second Hard coating has a columnar structure, and the crystal grains of the columnar structure have a compositional difference in the B component. Hard film-coated tool, which is a concrete.   The hard film-coated tool according to claim 1, wherein one part of nitrogen in the first hard film is substituted with carbon and oxygen, the whole nonmetallic component is 100, and the content of carbon element in atomic% is x, Hard film coating characterized by 0 <x ≦ 10, 0 <y ≦ 10, 0 <x + y ≦ 10, and nitrogen content 100−xy, where oxygen content is y tool.   3. The hard film-coated tool according to claim 1, wherein a part of the titanium in the second hard film is replaced with silicon, and when the total metal component is 100, the silicon content is expressed in atomic%. k, where 0 <k ≦ 20, and the titanium content is 100−h−k.   4. The hard film-coated tool according to claim 1, wherein the hard film having a compressive stress has a total film thickness of 10 to 30 [mu] m.   2. The hard film-coated tool according to claim 1, wherein the compositional modulation structure of the crystal grains of the second hard film has a B component composition difference of 10% or less in atomic%, and the compositional modulation in the compositional modulation structure. A hard film coated tool characterized in that crystal lattice stripes are continuous at the boundary.